Fluidized bed coking is a thermal conversion process in which heavy petroleum feeds are thermally cracked in a fluidized bed to form cracked vapor products and solids. In fluid coking and the fluidized bed coking process known as FLEXICOKING™, the thermally cracked vapors are typically passed through cyclones to separate coke fines entrained in the vapors and then through a scrubber. Some of the vapor formed by thermal cracking condenses and deposits on coke circulating in the thermal cracking unit and on various process equipment such as reactors, heat exchangers, reboilers, transfer lines, cyclones and fractionators. Subsequent thermal conversion of the condensed vapors converts them to coke. The process whereby coke is deposited on process equipment is known as fouling. The fluid coking process uses a fluidized bed reactor in which the thermal cracking reactions take place and a burner. The FLEXICOKING™ process uses a similar coking reactor together with a heater and gasifier. The specific configuration of the fluidized bed coking unit is not critical to the present invention.
Fouling is a major operational problem because fouled equipment must be shut down and periodically cleaned to remove coke deposits. Cleaning may be by mechanical means, such as pigging or by spalling/steam spalling, whereby the unit temperature is raised and lowered through several cycles causing coke deposits to break up due to differences in respective thermal expansion coefficients. Spalling may be followed by steam injection at high temperatures. Fouling has been addressed by the addition of chemical anti-foulants, use of scouring coke and by control of process conditions such as residence times and temperature differences, e.g., super heat.
Acoustic agglomeration is based on the use of sound to agglomerate small particles in the micron and sub-micron range present in aerosols. The thus agglomerated particles are more susceptible to conventional separation techniques such as cyclones, filters and the like, and to the return of agglomerated particles to the reactor phase. Acoustic sound waves are used to increase the relative molecular motion of the fine particles. This, in turn, results in more frequent collisions in which as least some of the particles stick together forming larger particles. The overall effect of acoustic treatment is to shift the median particle size of the aerosol to larger values. Acoustic agglomeration has been applied to particles in gases such as coat dust, fines from internal combustion engines and fly ash to make the particles larger and thus more susceptible to conventional separation techniques as noted above.